Alarm system for pneumatic tires

ABSTRACT

A system is provided for use with various types of vehicles employing pneumatic tires to signal the operator that the tire pressure is beyond a preset range. A spring-loaded pressure responsive piston is adapted to reciprocate within a valve structure in response to changes in tire pressure. If the piston is displaced one way or other beyond the predetermined range, air is released to operate a whistle detected by a sensing system on the vehicle which, in turn, generates a signal for the operator.

United States Patent 1 Barabino 1 June 12, 1973 ALARM SYSTEM FORPNEUMATIC TIRES [75] Inventor: William A. Barabino, North Reading, Mass.

[73] Assignee: Safety Research & Engineering Corp., North Reading, Mass.

[22] Filed: May 21, 1971 [21] Appl. No.: 145,624

[52] US. Cl 116/34 R, 73/1468, 137/227 [51] Int. Cl. 1360c 23/02 [58]Field of Search 116/34, 65, 70, 34 B;

[56] References Cited UNITED STATES PATENTS 1,411,714 4/1922 Durney eta1. 116/34 R 1,769,508 7/1930 l-larned 116/34 R 2,709,983 6/1955Divietro 116/34 R 3,203,246 8/1965 l-lorwitt et a1 116/70 X 3,276,41710/1966 Flowers 116/34 R Primary Examiner-Louis J Capozi Attorney-Morse,Altman & Oates [57] ABSTRACT A system is provided for use with varioustypes of vehicles employing pneumatic tires to signal the operator thatthe tire pressure is beyond a preset range. A spring-loaded pressureresponsive piston is adapted to reciprocate within a valve structure inresponse to changes in tire pressure. If the piston is displaced one wayor other beyond the predetermined range, air is released to operate awhistle detected by a sensing system on the vehicle which, in turn,generates a signal for the operator.

4 Claims, 5 Drawing Figures ALARM SYSTEM FOR PNEUMATIC TIRES BACKGROUNDOF THE INVENTION 1. Field of the Invention This invention relatesgenerally to tire pressure alarm systems and more particularly isdirected towards an electro-sonic system for warning of excessive gainor loss of pressure in a pneumatic tire.

2. Description of the Prior Art One of the major problems of highwayaccidents arises from tire failures, often caused by running a tire at apressure above or below a predetermined safe range. Not only is itdangerous to operate a tire beyond its optimum pressure, but suchpractice greatly reduces the useful life of the tire since the tire willwear unevenly and a faster rate if the pressure is not maintained withinspecified limits.

Various types of systems have been developed heretofore for the purposeof signaling the operator that the tire pressure of the vehicle isbeyond a specified range. Such systems have not been generally adoptedin practice, because of mechanical and electrical complexities, highcost of fabrication, instalation and maintenance as well as generalunreliability. Accordingly, it is an object of the present invention toprovide a new and improved tire pressure alarm system which is ofsimple, low cost construction, extremely durable and reliable and onewhich may be readily installed in existing vehicles.

SUMMARY OF THE INVENTION This invention features a tire pressure alarmsystem, comprising a cylinder mounted to the wheel and communicatingwith the interior of the tire and a springloaded piston mounted forreciprocation within the cylinder and formed with a passage therein. Avalve body encompassing an extension of the piston is formed with spacedports communicating with the atmosphere through a whistle wherebyexcessive axial displacement of the piston in either direction as theresult of a change in tire pressure will cause air to be released tooperate the whistle. A sensing system is mounted on the vehicle torespond to the sonic signal and alert the operator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view in sideelevation of a sonic signaling device made according to the inventionand installed in a tire,

FIG. 2 is a block diagram of the sensing circuit mounted on the vehicleand adapted to respond to the emitted sonic signal,

FIG. 3 is a circuit diagram of an amplifier employed in the sensingcircuit,

FIG. 4 is a circuit diagram of a filter circuit employed in the sensingcircuit, and,

FIG. 5 is a circuit diagram of a detector circuit employed in thesensing circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawings and to FIG. 1 in particular, the reference character generallyindicates a pressure responsive signaling device mounted to each wheel12 of a vehicle such as an automobile, bus, truck, airplane or the like.The device is adapted to emit a sonic signal whenever the tire pressuredrops below or rises above a predetermined safe operating range. In

general, the device 10 operates by actuating a whistle 14 through arelease of air whenever the tire pressure becomes excessively high orlow. The sound emitted by the whistle is sensed by means of a sensor 16mounted on the vehicle's chassis and, through circuitry described below,is adapted to actuate a visual or audio alarm to alert the driver.

The device 10, in the illustrated embodiment, includes a cylinder 18mountable within the tire chamber by means of a nut 20 threaded to aneck portion 22 of the cylinder extending through a valve stem aperture24 formed in the wheel rim 12. An O-ring 26 is provided to form anair-tight seal between the rim and the cylinder when tightened in placeby the nut 20.

The cylinder 18 is formed with one or more openings 28 communicatingwith the interior of the tire whereby the pressure within the cylinderbelow a piston 30 normally corresponds with the air pressure within thetire. The opening 28, however, is made small so that sharp changes inpressure which might, for example, be occasioned by the tireencountering a pothole in the road will not be transmitted into thecylinder 18. Rather, only those changes in pressure which occur over asubstantial period of time, such as perhaps five seconds or more, willbe transmitted. The piston 20 is slidably mounted within the cylinder 18and is formed with an elongated stem 32 extending upwardly through theneck portion 22 into a housing 34 supporting the whistle 14. The housing34 is detachably connected to the neck portion 22 as by threads 36 atthe lower end thereof.

The piston 30 is normally urged downwardly by means of a compressedspring 38 coiled about the valve stem. An O-ring 40 is provided aboutthe piston to form a sliding seal with the cylinder wall.

The piston 30, as well as its stem 32 is formed with a passage 42 openat its lower end to the cylinder 18 and closed at its upper end by meansof a conventional air valve 44. The valve 44 is used to add air to thetire as necessary, this being done by simply unscrewing the housing 34to make the air valve 44 accessible. The stem 32 is formed withtransverse passages 46 communicating with the longitudinal passage 42.

Upon reciprocation of the piston and stem, the passage 46 is adapted toregister with ports 48, 50 or 52 spaced along the upper portion of theneck 22. Assuming the air pressure within the tire builds up, this willcause the piston to move upwardly and, if the pressure is excessive, thetransverse passage 46 will align with the uppermost port 48 to releasepressurized air from the tire into the housing 34. The flow of air willmove upwardly through the housing and through the whistle 14 to emit asonic signal. At the same time, the whistle 14 itself will be displacedphysically upward under the force of the released air insofar as thewhistle is slidably mounted within the housing. Thus, the release of airnot only generates a sonic signal to be detected by the vehicle sensingsystem, but also pushes out the whistle to provide a quick visualindicator for the operator once he has stopped his vehicle. In practice,the body of the whistle may be brightly colored in red or orange, forexample, so that as the operator walks around the vehicle he may quicklyobserve which of the tires may be improperly inflated.

The device also serves to automatically correct an over-pressurecondition insofar as when the pressure is excessive, air is bled offthrough the port 48 until the tire pressure reduces sufficiently for thepiston to drop and the passage 46 to move back down into the safeoperating range between ports 48 and 50.

By using two low-pressure ports 50 and 52, two separate signals will begenerated which may be utilized to indicate loss of air to the operator.If the low-pressure condition is merely the result of improperinflation, normally only the port 50 would be opened and a single signalproduced. However, if the tire is leaking, pressure will continue todrop and ports 50 and 52 will open in succession producing two separatesignals. The time lag between the signals from the ports 50 and 52 maybe measured electronically by the sensing system and can indicate to thedriver the rate of loss of pressure in the tire. In this fashion, thedriver can make a judgement as to whether he may safely proceed to aservice station or stop and take an immediate corrective action.

The whistle 14 may be fabricated to produce an audio emission of a verydiscrete frequency to which the sensing system will be pre-tuned so asto respond only to that frequency. Preferably, the whistle is fabricatedto produce two or more simultaneous sonic emissions of differentdiscrete frequencies and the sensing system will be tuned to respondonly to that unique combination of frequencies. Also, the device may bedesigned to generate signals of different frequencies depending uponwhich port is opened by the stem 32. Thus, the frequency of theparticular signal may be processed electrically so that the drive willbe alerted as to the exact pressure condition.

Referring now to FIG. 2 of the drawings, there is illustrated a blockdiagram of a signal sensing circuit mounted to the vehicles chassis. Thecircuit includes a sonic sensing transducer 54 such as a microphonelocated on the vehicle in position to detect a whistle sound emitted bya device mounted on each wheel. In practice, a microphone 10 may bemounted in each wheel well or a single microphone may be centrallylocated to monitor a plurality of wheels depending upon the sensitivityof the pickup, distance and other factors.

In any event, the microphone 54 is adapted to detect an emitted soundand convert it to an electric signal which is them amplified by anamplifier 56, the output of the amplifier being fed into a bank of threeparallel filters 58, 58', 58". Each filter is designed to pass a singlepreset frequency. For example, the filter 58 is set to pass frequency F,which is the frequency of the high pressure signal produced by airescaping throughport 48, F being the low pressure warning signalresulting from the air escaping through port 50, and frequency Frepresenting the low pressure hazard signal resulting from air escapingthrough port 52. Depending upon the frequency of the particular signal,one of the filters 58 will pass a signal to an associated detectorcircuit 60, 60' or 60". Connected to each of the detectors 60 is a lamp62, 62 and 62" or other signaling device. The detector circuit employsthe output of the associated filter circuit to energize the lamp andlatch the circuit so that the particular lamp remains lit until manuallyturned off. In practice, the lamps 62 are mounted on the dash board ofthe vehicle where they may be readily observed by the driver. In placeof the lamps or in addition to the lamps other signaling devices such asbuzzers or the like may be utilized to attract the driver's attention.

Referring now to FIG. 3 of the drawings, there is illustrated a diagramof an amplifier circuit that may be used in the detecting system. Theamplifier 56 receives the output of the microphone 54 and includes apair of NPN transistors 64 and 66, the base of transistor 64 beingconnected to the microphone through a capacitor 68 and the emitter beingconnected to the base of the transistor 66. A variable resistor 70provides gain control, the amplifier output coming from the collector ofthe transistor 66.

In FIG. 4 there is a diagram of the filter circuit 58, the input beingthe output of the amplifier 56 fed through a capacitor 72 to the base ofa transistor 74. The emitter of the transistor 74 is connected to avariable tank circuit 76 the output of which is connected through acapacitor 78 and a variable inductance 80 to the base of a transistor82. The inductors of the filter circuit are tuned for the selectedfrequency which is to be detected, namely, frequency F1, F2 or F3. Itwill be understood that a filter circuit will be provided for eachfrequency and in the illustrated embodiment, three such circuits areprovided, each tuned to a particular frequency.

Referring now to FIG. 5 of the drawings, there is illustrated a circuitdiagram for the detector circuit 60 for controlling each lamp 62. Theinput to the detector circuit 60 is the output of the associated filtercircuit 58, the signal being fed through diode 84 and through anamplifier stage comprised of a pair of NPN transistors 86 and 88operating a relay 90. The relay 90 controls a switch 92 which opens andcloses a circuit to the lamp 62. It will be understood that a signal fedthrough the detecting circuit will energize the relay 90 to close theswitch 92, latching the circuit to the lamp 62 and providing the desiredindication.

Having thus described the invention, what I claim and desire to obtainby Letters Patent of the United States is:

1. A pressure warning device for a pneumatic tire, comprising a. ahousing formed with a cylindrical chamber therein one end of which beingin communication with the interior of said tire and the opposite endthereof being exterior of said tire,

b. a spring-loaded piston mounted in said chamber and being axiallymovable in response to changes in tire pressure,

c. said piston being formed with a passage communicating with theinterior of said tire,

d. at least one of said housing and said piston being formed with aplurality of axially spaced ports and the other of said housing and saidpiston being formed with at least one port, the piston ports being incommunication with said passage whereby excess movement of said pistonwill align certain of said ports to release air from said tire,

e. whistle means communicating with said ports and actuated by releaseof air from said tire and,

f. a check valve mounted directly to the outer end of said piston andcommunicating with said piston passage.

2. A pressure warning device according to claim 1 including an aperturedcover removably mounted over the exterior portion of said housing and amovable I member mounted to said cover and displaceable in response torelease of air from said tire from a hidden position in said cover to anexposed position.

3. A pressure warning device according to claim 2 wherein said member isa whistle.

4. A pressure warning device according to claim 1 wherein said housingis formed with a restricted orifice at the inner end thereof.

I. i i 4'

1. A pressure warning device for a pneumatic tire, comprising a. ahousing formed with a cylindrical chamber therein one end of which beingin communication with the interior of said tire and the opposite endthereof being exterior of said tire, b. a spring-loaded piston mountedin said chamber and being axially movable in response to changes in tirepressure, c. said piston being formed with a passage communicating withthe interior of said tire, d. at least one of said housing and saidpiston being formed with a plurality of axially spaced ports and theother of said housing and said piston being formed with at least oneport, the piston ports being in communication with said passage wherebyexcess movement of said piston will align certain of said ports torelease air from said tire, e. whistle means communicating with saidports and actuated by release of air from said tire and, f. a checkvalve mounted directly to the outer end of said piston and communicatingwith said piston passage.
 2. A pressure warning device according toclaim 1 including an apertured cover removably mounted over the exteriorportion of said housing and a movable member mounted to said cover anddisplaceable in response to release of air from said tire from a hiddenposition in said cover to an exposed position.
 3. A pressure warningdevice according to claim 2 wherein said member is a whistle.
 4. Apressure warning device according to claim 1 wherein said housing isformed with a restricted orifice at the inner end thereof.